Following Chlorine Burn, CDC Test Results Negative for Naegleria Fowleri Ameba in St. Bernard Parish Water System

Raised chlorine level credited with controlling rare ameba

February 11, 2014

BATON ROUGE, La. - Water samples taken in late January from the St. Bernard Parish water system have tested negative for the rare ameba Naegleria fowleri, meaning increased chlorine levels in the system have controlled the ameba, the Department of Health announced Tuesday.

The St. Bernard Parish water system was one of two water systems in Louisiana that tested positive for the rare ameba last year. Following a chlorine burn and a state mandate that required the parish to maintain a 1.0 milligram per liter free chlorine residual throughout the system for 60 days, LDH took two water samples from 11 locations along the system in late January. Testing by the federal Centers for Disease Control and Prevention confirmed this week that all 22 samples were negative for the rare ameba, which has killed three people in Louisiana since 2011.

LDH Secretary Kathy Kliebert said, "While the water in St. Bernard Parish was always safe to drink, these negative test results give us confidence that it is now safe for all uses. We will continue to work with parish leaders to monitor the system so that all families in the parish can feel safe."

Assistant Secretary for Public Health J.T. Lane said, "We are encouraged because these test result confirm that maintaining a certain free chlorine or chloramine residual in water systems can control this ameba and protect families. This is why LDH issued an emergency rule last year that we believe will make the water that we drink, bathe and play in safer."

Out of an abundance of caution, LDH will conduct additional sampling and testing in St. Bernard Parish later in the year as temperatures grow warmer, making water more inviting for the ameba. LDH still encourages people to take precautions, including using commercially distilled water or tap water that has been boiled and then cooled, when they are using a Neti pot for a sinus rinse.

NEW TESTING PROTOCOLS

Following input from national and international experts through the scientific work group, the Department and CDC implemented the multi-level testing protocols used successfully in Western Australia, whereby water samples are tested in a two-step process. The first step checks for the presence of a "thermophilic" ameba, or one that thrives in warm water. If thermophilic amebas are present, then a second test is run to confirm if these amebas are Naegleria fowleri, which is known to thrive in warm water. Amebas are very common in water and do not always present health risks. Naegleria fowleri is the ameba of most concern, given its rarity and the severity of the infection it causes.

In DeSoto and St. Bernard parishes, where this new testing protocol was first used, only one St. Bernard sample was positive for thermophilic amebas. Upon a more detailed second step of testing, this one sample also was negative for Naegleria fowleri.

This new protocol could ultimately be used as an initial screening mechanism for water systems to test for Naegleria fowleri, which will make the process less expensive and less time consuming. LDH is also working to become certified to conduct its own testing for the Naegleria fowleri at its Office of Public Health lab. Louisiana would be the only state to perform this kind of testing.

ABOUT NAEGLERIA FOWLERI IN LOUISIANA

In the fall of 2013, LDH announced that testing by the federal Centers for Disease Control and Prevention confirmed the presence of the Naegleria fowleri ameba in the water system in St. Bernard Parish and in Water Works System No. 1 in DeSoto Parish. The St. Bernard confirmation followed testing of various points on St. Bernard Parish's water system after Naegleria fowleri was determined by the CDC to be the cause of the death of a child who visited St. Bernard Parish in the summer of 2013.

LDH officials selected the DeSoto Parish Waterworks District No. 1 water system for testing in September 2013 because the area was the site of one of two 2011 Naegleria fowleri-related deaths in Louisiana. Following the confirmation in September 2013 that St. Bernard Parish's water system tested positive for the ameba, LDH officials tested the water in the DeSoto Parish Waterworks District No. 1 as a precautionary measure.

At the time of the 2011 deaths in DeSoto and St. Bernard parishes, officials could only confirm the presence of the ameba in the homes of the deceased, but not in the water systems. More advanced sampling technology is now available through the CDC. No known additional infections have occurred in DeSoto Parish, as incidences of infection are extremely rare. Exposure to Naegleria fowleri has historically occurred as a result of swimming or diving in warm freshwater lakes and rivers. An infection of Naegleria fowleri cannot occur by drinking water.

In response to the deaths and the positive test results, in November 2013, LDH issued an emergency rule requiring that water systems in the state maintain a higher residual disinfectant level and increase their number of sampling sites by 25 percent. Most drinking water systems in Louisiana will be required to meet this new higher standard by February 1, 2014. LDH also convened a scientific working group to gather as much information and research as it could about how to protect Louisiana families from the ameba.

Free chlorine or chloramine residual at 0.5 milligram per liter or higher will control the ameba, provided the disinfectant is present at that level throughout the water supply system continually.

LDH launched dhh.louisiana.gov/WaterFacts to provide the public with accurate information about the ameba. LDH is also accepting questions from the public for using a form on this website or via e-mail to DHHInfo@la.gov.